[CentOS] TCPWrappers + Sendmail = not working

I have set up entries in /etc/hosts.allow and /etc/hosts.deny as follows:

/etc/hosts.allow
sendmail : 10.0.0.0/255.0.0.0
sendmail : LOCAL

/etc/hosts.deny
sendmail : ALL

When I try to connect to port 25 from an Internet host via telnet, the
server still responds as usual.  The only difference I see is this in
my /var/log/maillog:

Apr 24 15:41:49 server sendmail[20691]: m3OKfna20691: tcpwrappers
(otherserver.example.com, xx.xx.xx.xx) rejection

How do I make tcpwrappers simply drop the connection?  I would prefer
to do this with TCP Wrappers, at least until we get our official
IPTables firewall policy worked out.

thanks

Sean